"Tu cântai foarte frumos."

Translation: You were singing very beautifully.

[ella_lavi]

FRUMOS= BEAUTIFUL

[BenYoung84]

or beautifully

[zj456]

In English, regular adverbs end in "-ly" (adjective + ly = beautiful + ly = beautifully). In Romanian, adverbs are invariant and take the form of the masculine singular adjective (adverb = m. s. adjective = frumos)

Therefore, frumos = beautiful OR beautifully (depending on what it applies to)

https://www.englisch-hilfen.de/en/grammar/adverbien.htm
https://en.wikipedia.org/wiki/Romanian_grammar#Adverbs